1. Field of the Invention
The present invention relates to a dispersant useful for pigment preparations for coloring polyolefins, and to pigment preparations prepared using this dispersant.
2. Discussion of the Background
Pigment preparations suitable for the coloring of polyolefins are already known. DE-B 12 39 093 describes carrier materials based on a mixture of an amorphous ethylene-propylene block copolymer having a viscosity of 5000-300,000 cp at 150.degree. C. and a low molecular weight, crystalline polypropylene. The use of polypropylene wax having a viscosity of 500-5000 cp at 170.degree. C. and an isotactic content of 40-90% by weight is described in DE-A 26 52 628. DE-C 42 36 337 reveals that certain polyacrylic acid esters are suitable as dispersants for pigments in organic media.
With the present prior art, however, when using such carrier materials in the coloring of polyolefins, it is not possible to completely prevent the occurrence of agglomerates. This is particularly disadvantageous in the preparation of colored polyolefin fibers, since pigment agglomerates can lead both to the blockage of the melt screens of the spinning extruder and to fiber breakage. Fiber breakages are extremely undesirable since they lead to a breakdown in production which is associated with considerable downtimes and substantial cleaning operations.